The proposed research will provide data on plasma skimming from in vitro experiments. Two geometries will be investigated, two bifurcations in series, and single bifurcations with unequal branch diameters. Measurements of red cell velocity and red cell flux in each branch will be performed using the red cell fluorescent labeling technique of Sarelius and Duling (1982). The data from this research will be helpful to in vivo microcirculationists and those researchers developing computer models to analyze hemodynamics in branching networks. In vivo microcirculationists will be better equipped to interpret their experimental results on network blood flow. The proposed experiments will provide computer modelers with data on the partition of red cells in vessel junctions. These data will fill one of the major needs to improve current models (Popel, 1980). This research is applicable to the physiological problems of blood flow regulation and oxygen delivery. It also has application to computer simulation experiments, which cannot be performed in vivo, in vascular disease research.